Selecting the best, or most suitable, SSD for your PC can be an overwhelming experience, but the rewards of blistering speeds or increased capacity warrant the effort. We’ve already covered What is an SSD? but since then, SSD prices have tumbled and capacities have risen. This is a practical guide to help you choose the best SSD for your setup.
To explain every nuance of SSD technology is unnecessary (and tremendously dull) so we’ll focus on the jargon and numbers used by manufacturers and vendors to entice you towards their products.
Let’s begin with some basics.
Why would I want an SSD?
Briefly, SSDs or Solid State Drives perform the same function as a normal S-ATA hard-drive, except they’re quicker. Imagine the S-ATA hard-drive as a turntable, and an SSD as an MP3 player. Now picture having to select 20 random tracks on a playlist using that technology – you can appreciate that using an MP3 player will be much faster.
Adding an SSD to a system increases overall performance and responsiveness, and whilst they’re useful for extending the life of an older machine, many users want to add them to new PCs.
New PCs will probably come with an SSD as standard, but the capacity is often rather small – 256GB or 512GB being the most common, so swapping this for a 1TB or 2TB SSD is an attractive proposition.
OK – I’m sold. How do I choose the right drive?
Compatibility is the keyword, so knowledge of your machine’s capabilities is critical. A useful tool to run is Speccy from Piriform, which will reveal details of your system’s hardware, including storage and motherboard specifics. Crucial also have a system scanner to suggest compatible parts.
Look at the existing drive in your PC. Googling the model number should let you know if you’re dealing with an SSD that is S-ATA or NVMe and if it has a 2.5″, PCI or M.2 form-factor.
Next is to do some research on your motherboard. Most manufacturers will provide forensic detail of the capabilities of their motherboards, but sometimes it’s best to reach for the screwdrivers. It’s not uncommon for motherboards to utilise both S-ATA and M.2 drives, so you may have a few options open to you. Remember that you’ll need a system with either AMD Zen3 or Intel Tiger-lake to use the faster PCIe 4 SSDs, so opt for a cheaper drive if PCIe 3 is the only option.
The M.2 Trap
Although we’ve mentioned this before, a common misapprehension prevails that M.2 equates to NVMe SSDS. M.2 relates to the physical shape of the drive and is available in both S-ATA and NVMe flavours. Ensure you match the drive and the socket.
A real world example
We’ll compare two of ADATA’s best-selling 2.5” S-ATA SSDs.
| ADATA SU650 240GB | ADATA SU630 240GB |
| NAND Flash: 3D NAND | NAND Flash: 3D QLC |
| Interface: SATA 6Gb/s (SATA III) | Interface: SATA 6Gb/s (SATA III) |
| MTBF: 2 million hours | MTBF: 2 million hours |
| Up to 500MB/s Read | Up to 520MB/s Read |
| Up to 430MB/s Write | Up to 400MB/s Write |
| 4K IOPS Read: 40000 | 4K IOPS Read: 30000 |
| 4K IOPS Write: 75000 | 4K IOPS Write: 65000 |
| TBW: 140TB | TBW: 50TB |
| Warranty: 3 Years | Warranty: 3 Years |
On a retailer’s shelf, the SU650 is the more expensive drive so it may surprise you to see that the cheaper SU630 has a higher read speed. It has a slower write speed but we’ll get to that later. The IOPS (input/output operations per second) figures have greater differentiation but as Sandisk claim “IOPS numbers published by storage device manufacturers do not guarantee real-world application performance”. The metric with the greatest difference is TBW (Terrabytes Written) which manufacturers use to predict the longevity of a drive. Another longevity metric you may come across is DWPD (Drive Writes Per Day) but many manufacturers (including Samsung) deem it to be archaic terminology.
TBW? More like GOWI!
TBW is ‘Terrabytes Written’ is a theoretical value intended to indicate how much data can be written during the lifetime of a drive before its memory cells fail. Performing a few calculations on our ADATA drives the TBW of the SU630 equates to roughley 46 GB/day against 128 GB/day of the SU650. Although the SU630 is cheaper and would outperform the SU650 in a read-only drag race, pushing a lot of data around with photography or video-editing applications will really shorten its lifespan. The SU650 is designed to handle much more work, which should give it a longer lifespan. The lesson here is that Read/Writes speeds are not everything.
NAND Flash: More is better, right?
Another difference between our ADATA drives is the NAND Flash in use. SSDs store data in NAND Flash memory cells and clever manufacturers can stack the NAND Flash to increase storage capacity.
Terms to spot on product packaging are SLC (Single Level Cell – 1 bit per cell), MLC (Multi Level Cell – 2 bits per cell), TLC (Triple Level Cell – 3 bits per cell) and QLC (Quad Level Cell – 4 bits per cell). PLC also exists but is rare – I suppose you can guess what it is.
The more NAND can increase capacity, it also kills data transfer rates. To modify the data on a drive, an SSD with QLC has to alter 4-bits compared to only 2-bits on a MLC. Some manufactures attempt to offset by using the badly named SLC-Caching, which uses unused areas of the SSD as pseudo-SLC NAND. This can be effective in increasing performance during low intensity day-to-day usage, but put a machine under stress until the SLC-Cache fills up and the QLC performance drops off a cliff. SLC-Caching will also misbehave if you’re running short of drive space too. Synology have a great deal more information on this phenomenon.
In our example, ADATA’s SU630 uses QLC and the SU650 uses TLC. From a retail perspective, there is less than £10 between these two drives but a vast difference in their performance potential.
The Big Tech Question short guide to SSD shopping.
Here’s our top 6 tips:
Do your research – Be sure what of what you’re buying. Consider how you use your machine and buy an SSD appropriate for that usage. Cheap consumer drives in your workstation are only going to end in tears but if your machine is only used for a bit of Excel and YouTube, then a bargain basement SSD will probably do the job. Look for the metrics we’ve discussed so you can compare products.
Price vs. Performance – The tired adage of ‘you get what you pay for’ is spot on for SSDs. However, using our information, you should be able to spot a bargain when it pops up.
Buy Big – More free space on an SSD makes for a healthier drive. Keep an eye on your capacities.
Beware of the downgrade – Before replacing an existing SSD, familiarise yourself with its capabilities before you accidentally purchase a new drive with a worse specification.
S-ATA may be better – After long-term storage drive and not fussed about speed? Don’t discount a S-ATA hard drive.
Install the software – Most drives come with management software to download to your PC. Find it and use it. It can upgrade firmware, maintain drive fitness and alert you when problems occur.
Backup – Irrespective of TBW, QLC or M.2, all drives can go bang so make sure you have a rigorous backup routine in place to avoid an OMG.
Now that you’ve got your brand spanking new SSD, you might need to migrate your current system over – but how do you do that? Check out our guide to clone your existing system to an SSD here.
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